Ferris Wheel Acceleration

1. The problem statement, all variables and given/known data
A Ferris wheel with a radius of 9.7m rotates at a constant rate, completing one revolution every 39s.
Suppose the Ferris wheel begins to decelerate at the rate of 0.19rad/s^2 when the passenger is at the top of the wheel.

Find the magnitude of the passenger's acceleration at that time.

2. Relevant equations
acp=v2/r=ω2r

3. The attempt at a solution
I don't understand the time they want me to use or where to start.